window.addEvent('domready', function() {
    init();
    var selector = $("selector_tipo");
    selector.addEvent('change',function(){
        var url = window.location.href;
        var i = url.indexOf('?');
        url =  url.substring(0,i);
        url = url + '?tipo='+this.value;
        window.location.href = url;
    });
});